Computed tomography (CT) is a non-invasive imaging technique, which is widely applied in medicine for diagnosis and surgical planning, and in industry for non-destructive testing (NDT) and non-destructive evaluation (NDE). So, it is significant for college students to understand the fundamental of CT. In this work, A CT
imaging system named CD-50BG with 50mm field-of-view has been developed for experimental teaching at colleges. With the translate-rotate scanning mode, the system makes use of a 7.4×10<sup>8</sup>Bq (20mCi) activity <sup>137</sup>Cs radioactive source which is held in a tungsten alloy to shield the radiation and guarantee no harm to human body, and a single plastic scintillator + photomultitude detector which is convenient for counting because of its short-time brightness and good single pulse. At same time, an image processing software with the functions of reconstruction, image processing and 3D visualization has also been developed to process the 16 bits acquired data. The reconstruction time for a 128×128 image is less than 0.1 second. High quality images with 0.8mm spatial resolution and 2% contrast sensitivity can be obtained. So far in China, more than ten institutions of higher education, including Tsinghua University and Peking University, have already applied the system for elementary teaching.
Volumetric region growing methods are usually used to extract volumetric region of interesting (VROI) from volume data. A volumetric region growing algorithm based on Fisher Distance (FD) is proposed in this paper. In order to reduce the effect of noise and strengthen the feature of volumetric region, and also to shift the anisotropic volume data to the isotropic, the preprocessing for volume data including 3D median filtering and interpolation is taken. The Fisher Distance (FD) is taken as the criteria to judge the growing condition. Furthermore, the formula for solving gray level standard deviations in FD is transformed to speed up the computation. Simulation results show that the volumetric region growing algorithm is not inferior to 2D region growing, while it has the superiority of saving time and reducing operation.